In recent years, a synthetic resin molded article with light weight and excellent impact resistance is used in various fields such as computer housings, light electrical components such as a cellular phone, and interior materials, and also is used for an automobile interior part. Many automobile interior parts such as instrument panels, center consoles and door trims are manufactured by initially, processing various synthetic resins to molded articles having desired shapes by an injection molding machine and the like, and then applying a color base coat containing a color material on the surface of the molded article to form a coating layer. If necessary, a plurality of coating layers are formed on the surface of the molded article, for example, by conducting a clear coating for improvement of weather resistance and wear resistance. Through these steps, the molded article having excellent weather resistance, wear resistance and decorative property are provided in the market.
However, as the synthetic resin molded article manufactured by such a method are treated by base coating or clear coating, the coating surface is eventually flat and even. Unfortunately, sufficient visual variations are not obtained on the surface of the synthetic resin molded article, resulting in poor designs.
When the synthetic resin molded article is used as an automobile interior part, the molded article on which an emboss pattern composed of fine concavo-convex shapes is molded to provide various design variations is widely utilized. For example, the patent document 1 discloses a method for providing a smooth texture by forming fine concavo-convex shapes on the surface of automobile interior parts and the like.
When base coating is conducted on a molded article with fine concavo-convex shapes, since the surface has different levels of heights in convex regions and concave regions, coatings flow into the concave regions, and thus it is very hard to make a coating thickness of convex regions and concave regions uniform. As a result, irregular-coating and irregular-coloring are formed.
Automobile interior parts are required to have functions which provide a comfortable internal environment for passengers. That is, the interior parts are required to have attractive appearances; high-quality design representations such as texture and color tone highlighted by providing a three-dimensional pattern and gloss; and good balance with designs of other interior parts.
Many of automobile interior parts include injection-molded articles derived from PP and ABS resin as substrates, and therefore, a high-quality appearance is created in the internal environment of an automobile by putting a high quality-looking material on the surface of the substrate. In recent years, since a trend of cost reduction is strongly increased, a low cost approach in which coating is directly conducted to molded articles of interior parts is often utilized. Lately, there are increasing demands for high-quality and individual decoration in these interior parts, and in many cases, the surfaces of interior parts are provided with decorations and covered with protective coating, and the surfaces of interior parts are treated by coating, transcribing by hydraulic pressure, decorating, and then glossy finish on the top surface layer.
Although various drawing patterns can be represented by coating and transcribing, they are only flat patterns. It is possible to represent designs with excellent three-dimensional patterns and more high-quality by combining drawing patterns with three-dimensional patterns. One example of these representations includes a method in combination with a step of applying fine concave and convex shapes by a metallic mold and a step of applying drawing patterns by transcription. In this method, matching of the concave and convex shapes to the drawing pattern is very difficult and the representation of concave and convex shapes is also very limited. As a result, three-dimensional patterns corresponding to the drawing patterns to be applied can not be obtained, and the design representations are largely limited.
Other example of factors for maintaining comfort of the internal environment of automobile includes prevention of discomfort for passengers such as noticeable stains caused by sebum from fingerprints on interior parts.
On the other hand, automobile interior parts are required to have functions such as safety and durability during driving in addition to providing a comfortable internal environment for passengers. To ensure safety during driving, antidazzling functions, i.e. functions to protect driver's eyes from reflective light in which incident light from the outside such as sunlight is reflected on the surface of the interior part or to prevent driving troubles with narrow range of view by entering reflective light into a front window are required. In durability, interior parts are required to be free from wearing and degradation with long-time use.
When the surface of the interior part is treated by glossy finish to create high-quality in consideration of comfort of internal environment, antidazzling function is impaired and a problem with safety is caused. Therefore, the surface of the interior part, which easily comes into driver's sight, such as an instrument panel is commonly ensured to have antidazzling property by matting on its whole or partial surface or forming fine concave and convex shapes on a clear coating layer to scatter light for matting. In a method for forming fine concave and convex shapes, patent document 2 discloses a technique in which fine concave and convex patterns are formed on a coating layer formed on the surface of the automobile interior part by indentation molding.
Although antidazzling property is ensured in the above method, design representations with excellent three-dimensional appearances and gloss appearances are limited. In a coating layer treated with a mat coat which is used to ensure antidazzling property, the mat effects are decreased gradually and a problem with durability is caused. As described in the patent document 2, in the case of fine concave and convex shapes for matting, matting only a desired part is difficult in terms of matching with a pattern. Thus, there is a problem that matting corresponding to decorative representations such as color pattern and drawing pattern cannot be conducted.